Earlier retained as a species as described (Cabrera, 1961; Gyldenstolpe, 1932), but swept under Hershkovitz’s (1962) broad concept of callosus and provisionally retained as such by Musser and Carleton (1993). Olds (1988; also Anderson, 1997) recognized C. venustus as separate from C. callosus proper, and defined it broadly to include boliviae and fecundus in Bolivia and NW Argentina (also see account of C. boliviae); others have more narrowly applied the name to the C Argentinian populations (e.g., Salazar-Bravo et al., 2001, 2002a; Vitullo et al., 1990) as distinct from fecundus (here = C. boliviae). Banded chromosomal comparisons with C. callidus provided by Vitullo et al. (1990), who considered the two, along with fecundus (here = C. boliviae) to form a closely related group, as did Espinosa et al. (1997). Salazar-Bravo et al. (2002a) similarly recognized a callosusvenustus clade, also embracing callidus and fecundus as species, although the taxa represented in these studies are not entirely equivalent.